Herbs, rarely shrubs, vines or trees. Leaves alternate or opposite, sessile or petiolate, simple, mostly entire. Stipules wanting. Inflorescence consisting of various clusters, terminal spikes or axillary heads. Flowers hermaphrodite or unisexual, actinomorphic, bracteate and bibracteolate. Tepals 5(—1), free or partly united, equal or the inner ones smaller, scarious, persistent. Stamens as many as the tepals and epitepalous; filaments free or united into a lobed tube; anthers 2- or 4-celled, with longitudinal dehiscence; staminodes present or wanting. Ovary superior, free or adnate to the base of the perianth, uni-locular, ovoid, ellipsoid or globose; styles 1—2 or wanting; stigma capitate, penicillate or the stigmatic branches 2—3, short or elongate. Ovules solitary or numerous, campylotropous, erect or suspended from the apex of an elongate basal funicle. Fruit a 1-seeded utricle, indehiscent, bursting irregularly or circumscissile or a 1- to several-seeded capsule. Seeds lenticular, oblong or reniform, orbicular, with or without an aril; testa crustaceous, smooth, punctulate or granulate. Endosperm copious, farinaceous. Embryo annular or horseshoe-shaped. About 800 species in 64 genera, widely distributed, most abundant in the tropical regions, especially in tropical America and Africa.